Freeze-drying of a purified human diploid cell rabies vaccine

A rabies vaccine prepared in human diploid cell strains was purified by continuous-flow sucrose density gradient centrifugation. The peak fractions containing 35-40% sucrose were diluted with a stabilizer consisting of degraded gelatine in a Tris-EDTA-buffer, and then inactivated with beta-propiolactone and freeze-dried to a residual moisture of approximately 2.5%. This vaccine was stable as proved by accelerated stability tests.